1. Field of the Invention
The invention relates generally to a method of fabricating a touch panel, and more particularly to a method of fabricating a capacitive touch panel.
2. Description of Related Art
Based on different ways of sensing, touch panels are generally categorized into resistant touch panels, capacitive touch panels, optical sensing touch panels, surface acoustic wave touch panels, and electromagnetic touch panels. The capacitive touch panels having advantages of excellent sensitivity, favorable reliability, and durability have been extensively applied in electronic devices.
Normally, the capacitive touch panel includes a plurality of first sensing series extending along a first direction and a plurality of second sensing series extending along a second direction. Each of the first sensing series includes a plurality of first sensing pads and a plurality of first bridge portions serially connected together, and each of the second sensing series includes a plurality of second sensing pads and a plurality of second bridge portions serially connected together. The first sensing pads and the second sensing pads together constitute a sensing array. When a user touches the touch panel with a finger, the first sensing series and the second sensing series of the touch panel cause a variation in capacitance on a position where the finger touches. The change of capacitance is transformed into a sensing signal, transmitted to a control circuit board, arithmetically processed, and thereby a proper instruction is output to operate the electronic device. Besides, the first sensing pads and the second sensing pads are made of indium tin oxide (ITO) in most cases, so as to enhance transmittance of the touch panel. However, overly high resistance of the ITO easily leads to low touch sensitivity of the touch panel. To resolve said issue, the first bridge portions or the second bridge portions are partially made of metallic materials instead of ITO according to the related art, and thereby the overly high resistance of the sensing series can be reduced.
The process of fabricating the touch panel is simplified in order to lower the manufacturing costs (e.g., fabrication of the uppermost insulating layer is omitted). However, given the uppermost insulating layer is not formed, the first bridge portions or the second bridge portions made of metallic materials are directly exposed to external surroundings, which easily results in metal oxidation and significant reduction of reliability and the life span of the touch panel. Additionally, if the contact pads that are located in the peripheral region of the touch panel and connected to external circuits are made of metallic materials, the metal contact pads, before being connected to the external circuits, are unavoidably exposed to the external surroundings directly, which is also likely to cause metal oxidation and significantly reduce the reliability and the life span of the touch panel.
Hence, how to reduce the resistance of the sensing series and prevent the metallic material from oxidizing without increasing the manufacturing costs are issues that need to be immediately resolved.